For the last 7 years I have been running my Honda XR650L with a Shorai LFX09L2-BS12 battery.
http://shoraipower.com/battery-specifications
If you like lithium/iron/phosphate (LiFePO4) batteries, any battery with a C.C.A. rating of 120, or higher, should easily start the Zongshen RX3. However, if you are running a lot of electrical accessories, you might need the higher Ah capacities provided by the lead/acid batteries.
I only run heated grips on my Honda XR650L.
The smaller, LiFePO4 batteries will easily crank the RX3 engine, but they lack the current reserve capacity of the larger, lead/acid batteries. Therefore, the smaller LiFePO4 batteries might be drained, and damaged, by the heavy current demand of running many electrical accessories.
__________________
Spud
"Never argue with an idiot. He will drag you down to his level, and beat you with experience."
Mark Twain
2015 Zongshen ZS250GY-3 (RX3)
2006 Zongshen ZS200GY-2 (Sierra 200)
2005 Honda XR650L
2004 Honda CRF250X
1998 Kawasaki KDX220
Mods made to my Zongshen ZS200GY-2:
http://www.chinariders.net/showthread.php?t=6894